The present invention relates to a process for monitoring the gas prefill pressure in hydraulic accumulators. The process comprises the steps of interrupting delivery of pressure to the oil side of the accumulator and emptying of the contents into the tank, measuring the gas temperature on the gas side of the hydraulic accumulator, measuring the gas pressure on the gas side of the hydraulic accumulator, and determining an actual value of the gas prefill pressure based on data relating to gas temperature or gas pressure by means of an evaluation device.
The operating properties of hydraulic accumulators are determined essentially by the prefill pressure selected. For the sake of perfect and dependable operation of accumulators and accumulator assemblies, monitoring must be carried out in the shorter periods between customary maintenance operations to determine if the constancy of the prefill pressure falls within acceptable variation limits. A monitoring process with the four process steps described above to be carried out for this purpose is conventional (cf. xe2x80x9cControle van hydro-accumulatorxe2x80x9d of the Dutch article xe2x80x9cContinue bewaking van de hydro-accumulator bespaart veel volgschadexe2x80x9d by T. Van Dale in xe2x80x9cPolytechnisch Tijdschrift,xe2x80x9d pp. 38-41, March 1992).
If the conventional process is performed as customary, protracted interruptions of operation and major difficulties arise, especially in cases in which a large number of accumulators are spatially mounted separate from each other in locations in large plants which are difficult to access.
Objects of the present invention are to provide a process which permits substantially simplified monitoring of hydraulic accumulators with a high degree of monitoring precision, even accumulators mounted in locations difficult to access.
In the process of the present invention, these objects are attained by measurement of the gas temperature and gas pressure up to the time of temperature equalization reached after emptying and telemetric transmission of data relating to gas temperature or gas pressure to a spatially remote evaluation device.
As a result of the telemetric data transmission of the present invention, a system is created allowing monitoring of the prefill pressure from a central measuring station in the shortest possible time and with the lowest possible personnel cost. The process of the present invention makes rapid and simple monitoring possible even in cases in which accumulators are difficult to access inside complex plants. Advantageous areas of application are accumulators and accumulator assemblies in iron and steel plants and rolling mills, in electric power generating plants, or, for example, machinery rooms with several machine assemblies. Simplification of monitoring makes it possible to carry out the monitoring processes in short periods of time, something of particular advantage if the hydraulic accumulators perform security functions. Additionally, the desirable high degree of monitoring precision is assured because data transmission takes into account the reaching of temperature equalization after emptying of the accumulator.
Telemetric data transmission may be effected by radio, instrument leads, via the telephone network, for example, or over the electric power supply grid by application of suitable modulation processes.
By preference, temperature values and pressure values generated by transducers coordinated with the thermometers and the pressure gauges on the manometer connection of the hydraulic accumulator are transmitted to a modem, one of which is provided on every hydraulic accumulator to be monitored. The temperature value and pressure value signals preferably are transmitted telemetrically by way of the modem of the hydraulic accumulator involved, without further processing, directly to the evaluation unit. On the evaluation unit, the appropriate computer program is run to calculate the actual gas prefill pressure corresponding to a reference temperature from the current temperature and pressure values. Alternatively, this calculation can be carried out at the hydraulic accumulator by an additional computer unit associated with a modem. Then, only the actual value of the gas prefill pressure is transmitted to the evaluation unit for subsequent presentation, for example, as a visual display, and/or for sounding an alarm or the like.
Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.